Many individual cytokines and growth factors have been evaluated for their therapeutic utility in the treatment of many varied diseases, disorders and injuries. Unfortunately, the results have been only partially encouraging. For example, PDGF-BB has proven to be useful in the treatment of diabetic foot ulcers; GM-CSF is marketed in Europe for both venous ulcers and diabetic foot ulcers; and HGH (human growth hormone) is marketed in the US for pediatric burns. Failures include BDNF, CNTF and IGF-1 which have all been evaluated in clinical trials designed to test their efficacy in treating ALS, each with disappointing results; TGFβ2 was unsuccessful in a phase 2 study for venous ulcers; and IGF-1 and PDGF combination therapy was unsuccessful in diabetic foot ulcers.
While is not clear why so many of these individual cytokines and growth factors have failed in the clinic, one theory is that the proteins were being administered in doses that were not physiologic, i.e. very high doses compared to the physiologic levels normally found in vivo. Also, because of the complex interaction between cytokines and growth factors in a given physiological niche, the application of just one factor, especially one at abnormally high levels, cannot recreate the physiological niche and may, in fact, grossly disturb its delicate balance.
Compounding their limited success in the clinic, cytokines and growth factors and other protein-based therapeutics are typically more difficult to administer to patients than other pharmaceuticals. Because the efficacy of a protein is related to its shape, protein-based therapeutics cannot be subjected to conditions that could cause the unfolding, or denaturing, of the protein or proteins contained therein. Consequently, special care is necessary in the preparation, storage, and administration of protein-based therapeutics.
In addition to avoiding any denaturation of the protein, it is often desirable to be able to control the amount of the protein administered to a patient over time. This helps to avoid protein concentrations within the patient that are undesirably high or low or that fluctuate too much from a desired level, and instead helps maintain a steady level of the therapeutic in the patient. To address this, sustained-release formulations for many therapeutics, including protein-based therapeutics, have been or are currently in development. Sustained-release protein-based therapeutics can be administered by a variety of methods, including but not limited to oral delivery of tablets or capsules, inhalation of powders, implantation, incorporation into a matrix, or topical application of an encapsulated therapeutic from which the protein is gradually released over time.
The preparation of such sustained-release formulations are varied. One process includes mixing the protein with an organic solvent. For example, a powder formulation may be made by spraying a mixture of the protein and an organic solvent into liquid nitrogen. Another process involves mixing the protein with a solution of a bioerodible/biodegradable polymer in an organic solvent, resulting in the formation of microparticles which contain the protein and the polymer by coagulation of the mixture. In yet another process, proteins, powdered formulations, or microparticles can be mixed with an organic solvent to produce a liquid or gel which may be injected into a patient or applied topically. Unfortunately, drawbacks to using organic solvents are their tendency to cause protein denaturation.
Additives have been used to stabilize proteins in the presence of a denaturing organic solvent. These additives include surfactants (see U.S. Pat. No. 5,096,885), amino acids (see U.S. Pat. No. 4,297,344), polyols (see U.S. Pat. No. 5,589,167), natural polymers (see WO 8903671), synthetic polymers (see Pharm. Res. 8:285 291, 1991), and metals (see U.S. Pat. No. 6,191,107 B1), each of which is incorporated herein by reference.
To date, no protein-based therapeutic agent (i.e. cytokines and growth factors) is available that effectively recreates or mimics the complex combination and physiologic levels of physiologically relevant cytokines and growth factors found naturally in the body in healthy and disease or injury states. Every protein-based therapeutic currently available administers a dose many, many times higher than the levels that the cytokines or growth factors are normally found in the body. In addition, no one has yet been able to administer these physiologically relevant cytokines and growth factors at physiological levels. Further, no one has yet been able to administer these physiologically relevant cytokines and growth factors at physiological levels in a sustained-release formulation. Therefore, Applicants present herewith for the first time the instant invention whose object is to satisfy the unmet medical need of providing physiologically relevant growth factors and cytokines at physiologic levels (CFS compositions), and in some instances, delivering those physiologically relevant growth factors and cytokines at physiologic levels using a sustained-release formulation (SR-CFS compositions).